Fluid driving system for vehicles



April 18 1961 G. J. BAUDHUIN Erm. 2,980,193

FLUID DRIVING SYSTEM FOR VEHICLES Filed May 16, 1959 2 Sheets-Sheet 1April 18, 1961 G. J. BAUDHUIN ETAL 2,980,193

FLUID DRIVING SYSTEM FOR VEHICLES 2 Sheets-Sheet 2 Filed May le, 1959nited States Patent FLUID DRIVING sYsrnM ron VEHICLES George J. Baudhuinand Arnold C. Petersen, Sturgeon Bay, `Wis., assignors to MarineTravelift dr'Engineering, Inc., Sturgeon Bay, Wis., a corporation ofWiscousin Filed Nov. 16, 1959, Ser. No. 853,262

15 Claims. (Cl. 18d-6.48)

This invention relates to an hydraulic drive system for a self-propelledvehicle.

An Aimportant object of this invention is to provide an hydraulic drivesystem for a vehicle having a plurality of drive wheels, which drivesystem is arranged -to provide a differential action to enable the drivewheels to rotate at relatively different speeds during turning of thevehicle and which will prevent the loss of pressure to one of the wheelsin the event the other wheel loses traction or begins to spin.

Another object of this invention is to provide an hydraulic vehicledrive system of the type having a fluid drive motor connected to theWheel, a remote pump for supplying fluid to the motor, and a controlvalve for reversibly controlling the ow of fluid from the pump to themotor, which drive system has brake valves located adjacent the drivemotors and operated under the control of the remote control valve forregulating the ilow of uid to and from the drive motor to retardrotation of the motor when the control valve is shut oir.

Yet another object of this invention is to provide an hydraulic drivesystem in accordance with the foregoing object and which is operative toeect braking of the hydraulic drive motor in either direction ofrotation of the motor.

These, togther with various ancillary objects and advantages of thisinvention will be more readily appreciated as the same becomes betterunderstood by reference to the lfollowing detailed description whentaken in connection with accompanying drawing wherein:

-Figure 1 is a side elevational view of the self-propelled vehiclehaving the drive system of the present invention applied thereto;

Fig. 2 is a schematic view illustrating the drive system with thecontrol valve in the neutral position;

Fig. 3 is a schematic view of the drive system with the control valvesmoved out of the neutral position thereof to effect driving of the motorin one direction; and

Fig. 4 is a fragmentary sectional view taken on the plane 4 4 of Fig. 1.

The vehicle drive system of the present invention is herein shownapplied to a self-propeiled vehicle of the type generally shown inPatent No. 2,909,298 to George J. Baudhuin, to which reference is madefor a more detailed description of the vehicle. In general, vthe vehicleincludes a front generally U-shaped frame 1i), a rear U-shaped frame 11and spaced side members 12. The front frame is secured to the forwardends of the side members 12, and the 'rear frame 11 is attached to asleeve 13 which is slidable along the side members and is adapted to belocked in adjusted position by a screw 14. The rear vehicle supportwheels 15 are mounted by a yoke 16 on the sleeves 13 and the frontwheels are journaled in yokes 18. The front yokes iti are mounted forturning movement about an upright axis preferably aligned with the frontframe 10, and turning of the front forks iSl effected by steeringcontrol units 21. Winches 22v are vFluid under pressure is supplied tothe hydraulic drive motors 24, the steering cylinders 21, and the winchdrive motors 22 from one or more Afluid pumps herein shown three innumber and designated 31a-31e. The pumps have their inlets connected toa reservoir 32 and are driven by an engine 33 also mounted on thevehicle.

The hydraulic drive system for each drive wheel includes a four-Way iiowreversing valve 41 and a pair of brake valves 42 and 43. The valves foreach cylinder are similar and like numerals are used to designatecorresponding parts of the drive system for the several wheels. In theembodiment herein illustrated, a pair of drive wheels are provided, oneat each side of the self-propelled vehicle, and,'for convenience, thecontrol and brake valves of the hydraulic system associated with theright hand Wheel are designated by the letter R and the control andbrake valves of the drive system associated with the left hand wheel aredesignated by the letter L. Although the vehicle shown has two drivewheels, it

is to be understood that the drive system is adapted, byy duplicationAof the controls, to drive al1 four wheels ofl the vehicle.

The control valves 41 are conventional four-way three I positionedvalves of the type in which the work ports are inv open communicationwith each other and with the reservoir return line when the valve is inits neutral position. As diagrammatically shown in Fig. 2, the valves 41have an inlet section 45 formed with a pressure inlet port 46 and a lowpressure return port 47. The inlet port 46 is connected as through apipe 4S with the vdischarge side of one of the pumps 31, and the returnport is connected through aline 49 with the reservoir 32. A relief valve50 is mounted in'the inlet section between the inlet and return ports 46and 47 and is arranged to open to by-pass the pump discharge, when thepressure at the inlet exceeds a preselected value. The working section47 of the valve has a valve bore 51 therein and a spool valve member 52slidable in the bore. The spool valve member is normally returned to itsneutral position shown in Fig. 2 by a return spring 53. l Fluid underpressure from the pressure inlet 46 is supplied past a checky valve 54to spaced pressure ports 55 and 56. Re#

turn ports 57 and 58 are communicated with each other` through a passagel59, and are connected through a pas-v sage 60 with the return port 47of the inlet section. The valve has controlled or work ports 61 and 62and, in the neutral position of the valve, the valve spools block thepressure inlet ports 55 and 56 and communicate the Work ports 61 and 62with each other and with the return passage 60. As is conventional, anoperating lever designated' 64 is pivotally attached to an ear 65 on thevalve casing and to the spool member 52 for selectively moving the same.When the spool valve member is moved in either direction from itsneutral position, fluid under pressure is supplied to one of the workports` and the other work port is connected to the return line. Thus,

when the spool valve member is moved to the left fromA its neutralposition shown in Fig. 2 to the position shown in Fig.- 3, iiuid underpressure from the pressure port 55 s supplied to the work port 61 andthe work port 62 is communicated to the return line 49. Conversely, whenthe spool valve member is moved to theright from its assegna A Sineutral position shown in Fig. 2, fluid under pressure will be suppliedto the other work port 62. The work section 47 of the particular valveherein illustrated is arranged to be connected in multiple with other valve work sections and, for this purpose, has an auxiliary pressure port68 which is in continuous communication through passage 69 with thepressure inlet do. Fluid under pressure from the auxiliary pressure port68 is continuously supplied to an auxiliary pressure outlet 7l and isintermittently supplied to a second auxiliary outlet '72 only when thevalve stem is in its neutral position. An auxiliary return line '73communicates with the return passage di). Thus, a control valve (notshown) for other equipment such as the winch 22 may be connected to thevalve 41.

r[he work ports 61 and 62 of the control valves are connected throughconduits 81 and 32 to the respective hydraulic motor 24. The length ofthe conduits Si and 8.?. will vary dependent upon the relative distancesand are generally formed in whole or in part at least of a resilienttubing such as rubber in order to accommodate relative movement betweenthe parts of the vehicle. The brake valves 42 and 43 are connected inthe conduit Si and 32 respectively and are advantageously mountedclosely adjacent the hydraulic motors 24 and conveniently directlythereon as best shown in Fig. 4. ri`he brake valves 42 and 43 areidentical in construction and like numerals are used to designatecorresponding parts. Although the brake valves are herein shown asseparate units, it is apparent that the valves could, if desired, beformed in a single body. The brake valves are arranged to be operatedunder the control of the control valves il so as to close and block flowfrom the respective hydraulic motor, when the control valve is in itsneutral position, and to automatically open and permit free ow of iluidto and from the motor when the control valve is moved out of its neutralposition. The brake valves each include a rst port 84 which is connectedto a respective one of the conduits 81 and ft2 leading to the controlvalve 4l and a second port 85 which is connected through a respectiveone of passages 86 and 87 to the hydraulic drive motor. Flow between theports 84 and 35 is under the control of a check valve 91 and a pilotoperated valve 92 which are connected in parallel with each other. Thecheck valve 91 is biased by a spring 93 to a position blocking owthrough the check valve port 94 and is arranged to move to its openposition and permit flow from the port 84 to the port 85, and to closeto prevent return flow. The bypass valve 92 includes a spool 96 which isyieldably urged by a spring 97 to a position blocking flow through theby-pass port 98. Provision is made for opening the by-pass valve 92 inone of the conduits such as 81, to permit return flow from the uid motor24, when fluid under pressure is supplied to the motor through the otherconduit 82. For this purpose, rst and second pistons lill and 102 areprovided on the valve member 92 at the end opposite the spring 97. Aplug w3 slidably receives the piston N2 and segregates the area A-l ofthe piston 101 from the area A-2 of the piston 102. Fluid under pressurefrom one conduit such as 82 is supplied through a tube 166 and pressureinlet port 107 to the area A-l of the valve member of brake valve 42and, similarly, fluid under pressure from the other conduit 81 issupplied through a conduit S and the aforedescribed pressure port 107 tothe area A-l of the valve member of brake valve 43. Thus, when thecontrol valve 41 is moved to a position such as shown in Fig. 3 tosupply uid under pressure to one of the conduits such as 81, the lcheckvalve 91 in the associated brake valve 42 will open and permit flow tothe motor and, simultaneously, fluid under pressure will be suppliedfrom the conduit Si through tube 198 to open the bypass valve. intheconduit 82 which then functions as the return line for the motor 24.When the control valve 41 is returned to its neutral position, theconduits Si and 82 are corn-v municated with the reservoir 32 and underthese conditions, the pressure on the area A-l is insufficient to openthe by-pass valve in either of the brake valves 42 or 43. This cuts offthe flow of fluid from the hydraulic motor 24 and retards or stopsrotation of the hydraulic motor and its associated wheel i7.

In accordance with the present invention, provision is made forgradually retarding rotation of the pump when the control valve is movedto its neutral position, to prevent the build-up of excessive pressuresand stresses in the drive system. For this purpose, duid under pressurefrom the second or motor outlet port of each brake valve is suppliedthrough a passage liti to the area A-Z on the piston W2. The area A-2 isselected so as to be relatively small as compared to the area A4. sothat the bypass valve 92 is moved to its open position in response topumping action of the associated hydraulic motor 24, only when thepressure reaches a relatively high value substantially in excess of thenormal operating pressure supplied by the pump 3i. rlhe pressure appliedby the spring 9? is made adjustable by a screw 112 so as to enableadjustment of the pressure in the lines S6 or 87 required to effectopening or" the bypass valve in response to pumping of the hydraulicmotors 2e, and hence control the amount of braking action applied to themotors.

In accordance with the present invention, the drive system is alsomanged to enable the drive wheels to rotate at relatively differentspeeds as is necessary due to the markedly different turning radius ofthe wheels when the vehicle is turning. The wheel at the inside during aturn will rotate slower and, since the pumps 3E are operated at the samespeed, the pressure on the drive motor Z4 :for the inside wheel wilibuild up substantially above the pressure on the drive motor for theoutside wheel. This tends to cause a slow spinning of the inside wheelduring the turn. ln order to overcome this problem, a restricted by-passtube 12d is connected to the work conduits Ell of the control valves MR'and elle and a second restricted bypass tube nl is connected to the Workconduits S2. The tubes E21 and iZZvprovide restricted communicationbetween the conduits di and between the conduits Since the controlvalves are operated in unison, as by a linkage i223 to simultaneouslysupply duid under pressure to either the con-l duits 3l or for both theleft and right drive motors, an increase in pressure in one of theconduits such as 81 for one drive motor such as 24h will be partiallyrelieved by llow through the restricted tube i263v to the conduit dllfor the other drive rnotcr 245K. This not only reduces the pressure onthe wheel drive motor a the inside during7 the turn, but also suppliesadditional lluid under pressure to the motor for the outboard wheel soas to drive the latter relatively faster,

The diierential in the rate of turning of the wheels is relatively low.In order to prevent complete loss of pressure and hard stalling of thevehicle when only one wheel looses traction, the tubes 12d and 12 areselected so as to be small as compared to the conduits 81 and 82 and toprovide a relatively high impedance to the ow of full pump dischargethrough the tubes. Thus, a small tube, for example a onequarter inchtube, will be sufficient to relieve the pressure which builds up on onemotor during a turn. However, if one motor completely looses tractionand begins to spin, the tube will restrict flow therethrough from theother line and thus maintain sufcient pressure on the other motor toeffect driving of the vehicle. The by-pass tubes 12@ and 121 can beadvantageously located closely adjacent the control valves 4U.' and 411KSince the control valves are mounted in side-by-side relation, thisminimizes the length of the by-pass tubes.

From the foregoing it is thought that the construction and operation ofthe driving system will be readily understood. When the control valves41 are in their-neutralV position, the conduits 81 and 82 arecommunicated to the reservoir so that the pressure on the areas A-1 ofthe by-V on'the hydraulic motors when the control valve isv in its`neutral position, to retard rotation ofk the motors and gradually stopthe vehicle when it is in motion, and to hold the vehicle in its stoppedposition on an incline. However, when the control valve is'v moved ineither direction from its neutral position, such as tothe left as viewedin Fig. 3, fluid under pressure is supplied to one of the conduits 81.The fluid opens the check valve 91 in the associated brake valve 42 andpasses to the hy-A draulic motor 24 to drive the same in one direction.The lluid under pressure from the conduit 81 is also supplied to thetube 108 and area A1 on the by-pass valve of brake valve 43 so as toopen the return line and permit i'luid from the hydraulic motor to flowthroughv conduit 82 back to the reservoir. Conversely, when the controlvalve is moved in the other direction from its neutral position, itsupplies fluid under pressure to the conduit 82 and communicates theconduit 81 to the reservoir 32 so as to drive the hydraulic motor 24 inits other direction. In this manner, the brake valves are operated totheir open position when the control valve is posi-V tioned to drive thehydraulic motor in either direction and, when the control valve is initstneutral position, the brake valves will maintain a preselectedrelatively high back pressure on the hydraulic motor to preventVrotation of the motor in either direction and thereby providebi-directional braking action. During a turn, the pressure which buildsup on the motor for the inside wheel is partially relieved by flowthrough one of the tubes 121 or 122 to aid in driving the outside motor.However, if one wheel loses traction and begins to spin, the tubes 120and 121 restrict the ow therethrough so as to maintain pressure on theother motor to drive the other wheel.

We claim:

l. An hydraulic drive system for a vehicle having at least one drivewheel comprising, a pump, a lluid motor connected to said drive wheel, aflow reversing valve connected to said pump and having first and secondow passages connected to said motor, said reversing valve being operableto selectively supply fluid under pressure from said pump to said firstand second flow passages, first and second brake valve means in saidfirst and second flow passages for controlling flow therethrough, andmeans responsive to the application of uid pressure from said pump toone of said flow passages for opening the brake valve means in both ofsaid flow passages to drive said motor from said pump and responsive totermination of fluid pressure from the pump to both ow passages forclosing said brake valve means to stop the motor.

2, An hydraulic drive system for a vehicle having at least one drivewheel comprising, a pump, a uid motor connected to said drive wheel, aow reversing valve connected to said pump and having first and second owpassages connected to said motor, said reversing valve being operable toselectively supply iiuid under pressure to said first and second flowpassages, iirst and second brake valve means in said first and second owpassages normally urged to a position blocking flow through said owpassages, a first means responsive to the application of a rstpreselected pressure from said pump to said one of said ow passages foropening said brake valve means to thereby effect driving of said motorfrom said pump, and a second means responsive to a second preselectedpressure in said iiow passages produced when said motor is driven bysaid drive wheel for opening said brake valve means to gradually stopsaid motor.

3. Anhydraulicdrive system` for a vehicle having at least one drivewheel comprising, a pump, a fluid motor connected to'said drive wheel, aow reversing valve connected to said pump and having first and second owpassages connected to said motor to reversibly control the ow of fluidthereto, first and second brake valves in said rst andy second passages,said brakevalves each including a first valve means operative to open topermit.

ow from the pump to the motor through the respective passage and toclose to prevent return flow, said brake valves each including a secondvalve means connected in parallel to the respective first valve meansand normally urged to a closed position, andV means operative inresponse to the, application of uid under pressure from the pump to oneof said passages for operating the second valve meansv in the otherpassage-toitsl open position.

4. An hydraulic drive'system for a vehicle having at least one drivewheel comprising, a pump, a fluid motor connected to said drive wheel, aflow reversing valve connected to said pump and having first and secondflow passages connected to said motor for reversibly controlling theflow o f fluid thereto, iirstand second vbrake valves in said first andsecond passages, said brake valves each including a first valve meansoperative to open to permit flow from the pump to the motor through therespective ilow passage and to close to prevent return flow, said brakevalves each including a second .pressure operated valve means normallyurged to a Aclosed position, a iirst means operative in response totheapplication of a first preselected pressure from said pump to one ofsaid4 flow passages for operating said second valve means in the otherpassage to its open position, and a second means operative in responseto a second relatively high pressure vin one flow passage produced whensaid motor is driven by the drivewheel for opening the second valvelmeans in that flow passage to thereby gradually stop the motor.

5. An hydraulic drive system for a vehicle having at least one drivewheel comprising, a pump, a uid motor` connected to said drive wheel, aow reversing valve connected to said pump and having first and second owpassages connected to said motor to reversibly control lovvk thereto,4first and second braking devices in said first and second passages,said braking devices each including a check valve operative to open topermit ow from the pumpto the motor and to close to prevent ow from themotor to the pump, said braking devices each including a by-pass Valveconnected across the respective check valve, means yieldably urging saidby-pass valves to a closed position, uid pressure responsive operatingmeans on each by-pass valve, and means communicating when fluid underpressure from the pump is supplied to the other flow passage.

6. An hydraulic drive system for a vehicle having at least one drivewheel comprising, a pump, a liuid motor connected to said drive wheel, aow reversing valve connected to said pump and having first and secondilow passages connected to said motor to reversibly control oW thereto,iirst and second braking devices in said first and second passages, saidbraking devices each including a check valve operative to open to permitflow from the pump to the motor and to close to prevent fiow from themotor to the pump, said braking devices each including a by-pass valveconnected across the respective check valve and having a valve membermovable from a closed position to an open position, means yieldablyurging the valve members to a closed position, means defining first andsecond areas on each of said valve members, means communicating witheach ow passage at a point between the flow reversing valve and theby-pass valve therein for applying uid pressure from the pump to said ,Yassesserr i rstarea on the bypass valve member inthe 'other ow passage,and means communicating with each ow passage, ata point between theby-pass valve thereonY and the fluid motor for applying fluid pressureto saidsecond area on the by'pass valve member in the respective owpassage.

7. An hydraulic drive system for a vehicle having at least'one drivewheel comprising, a pump, a fluid motor connected to said drive wheel, aow reversing valve connected to said pumpand having rst and second owpassages connected to said motor to reversibly control flow thereto,first and second braking devices in said'rst and second passages, saidbraking devices each including a check valve' operative to open topermit ow from the pump to the motor and to close to prevent ow from themotor to the pump, said braking devices each including a by-pass valveconnected acrossv the respective check valve and having a valve membermovable from a closed to an open position, means yieldably urging saidvalve member to its closed'position, means defining tirstl and secondareas on each of' said valve members, means operative when the reversingvalve supplies fluid under pressure from the pump to one ow passage forapplying fluid pressure to the iirst area on the by-pass valve member inthe other flow passage to open the same, and means operative when themotor is driven by the wheel and pumps fluid into one llow passage forapplying pressure to the `second area; on the by-pass valve member inthat passage to open that by-pass valve and relieve the pressure inexcess of a preselected valve to thereby gradually stop the motor.

8. The combination of claim 7 wherein said rst area on each valve memberis large as compared to said second area.

9. An hydraulicdrive system for a vehicle having at leasttwo drivewheels comprising pump means, a Huid motor connected to each saidwheels, a pair of flow reversing valves connected to said pump means andeach having supply and return conduits connected to a respective one ofsaid fluid motors, said flow reversing valves being selectively operableto supply fluid under pressure from said pump means to said supplyconduits to drive the Wheels'in one direction and to supply fluid tosaid return conduits to drive the Vehicle in the other direction,conduit means communicating said supply conduits of' said pair of owreversing valves with each other, said conduit means defining a cross-owpassage having a flow impedance which is high as `compared to the owimpedance of saidV supply conduits to restrict the rate of iiow of fluidfrom one supply conduit to the other supply conduit.

10. An hydraulic drive system for a vehicle having a pair of drivewheels comprising, a iluid motor connected to each of said wheels, pumpmeans, first and second flow K control means connected to said pumpmeans and each having supply and return conduits connected to a respective one of' saidiiuid motors, said owcontrolmeans being selectivelyoperablev to supply iluid under pressure from said pump means to saidsupply conduits to drive said wheels-in one direction and to supplyfluid from said pump means tosaid return conduits to drive said vehiclein the other direction, and first and second cross-flowconduits'respectively communicating the supply conduits of said rst andsecondV motors and the return conduits of said first and second motorswith each other, said cross conduits having a ow impedance which is highas compared to the ow `impedance of said supply and return conduits torestrict the rate of flow of fluid from the supply and return conduitsof one motor to the supply and return conduits of the other motor.

11. An hydraulic drive system-for a vehicle comprising at least twodrive wheels-located at opposite sides of the vehicle, a uid motorconnected to each wheel, pump means, first and second control valvesconnected to said pumpl means and each havingl supply and returnconduits connected to` a respective one of said iiuid motors, saidcontrol valves being selectively operable to supply iiuid from said pumpmeans to said supply conduits to drive said motors in one direction, arst valve means in each conduit operative to open and permit ow from thepump to the motor and to close to prevent return ow, a second pressureoperated valve means in each conduit connected across said iirst firstVvalve means and normally urged tok a closed position,` means operativein response to the application ofuid pressure to one of said conduitsfor operating the second valve means in the other conduit to its openposition, and first and second cross-flow conduits respectivelycommunicating said supply conduits of said rst and second motors andsaid return conduits of said first and second motors with each other.

12. The combination of claim l1 wherein said cross conduits have a ilowimpedance which is high as compared to the ow impedance of said supplyand return conduits to restrict the rate of ow of uid from the supplyand return conduits of one motor to the supply and return conduits ofthe other motor.

13. The combination of claim l2 including means for operating saidcontrol valves in unison.

i4. The combination of claim 1l wherein said first and second Valvemeans in each conduit are located closely adjacent said motors.

15. The combination of claim 14 wherein said crossflow conduits arelocated closely adjacent said control valves.

No references cited.

